In 1980, the National Fire Prevention Association determined that 77% of residential fires originated in the kitchen and the leading cause was traced to the range or cooking unit. An alarm device that would warn the stove operator when a burner on an electric range has been energized but is not in use could help prevent such fires. The alarm system would also serve to save energy, lengthen the time of service of the burner and aid the blind and visually impaired.
Norris, in U.S. Pat. No. 4,334,145, issued June 8, 1982, discloses an alarm system for an electric range with a mechanically operated switch under each burner which deactivates the alarm when a cooking utensil is on the burner and the burner is energized. Because of the proximity of the alarm switching means to the burner, this arrangement can cause heat to be conducted down into the range damaging the wiring and the sensing switch. Also, the lever and fulcrum system used to operate the switch is susceptible to damage due to food or grease which may be spilled on the burner.
Nashawaty in U.S. Pat. No. 4,446,455, issued May 1, 1984, describes an alarm system useful in both electric or gas ranges and which is actuated when a burner is energized when there is no cooking utensil on the heating element. However, the alarm system disclosed is activated by a power source which is separate from the burner, such that the alarm system could fail and not emit a signal even when a burner is energized without a utensil placed on it. As in the Norris patent, there are also the problems of heat conduction into the range and damage to the switch if food is spilled into the burner.